Tag Archives: predation

The warmer the dangerouser, at least if you are a caterpillar

by Piter Kehoma Boll

Scientist all over the world agree that species diversity is higher at the tropics than at polar regions, i.e., the closer you get to the equator, more species you will find. But apart from making food webs more entangled, does it increase the overall number of interactions that species experience? Afterall, despite the increase in species richness, the population size usually decreases. For example, while there are hundreds of different tree species in the Amazon forest, the number of individuals of each species is much lower than the number of individuals of a species in a temperate forest in Europe.

In order to test whether an increase in species richness would also mean an increase in biotic interactions, a group of ecologists all over the world engaged in a worldwide experiment using nothing else but small fake caterpillars made of plasticine. The small models were placed in different areas from the polar regions to the equatorial regions and the number of attacks that they suffered were counted and grouped according to the type of predator, which was usually identifiable based on the marks left on the models.


A fake caterpillar in Tai Po Kau, Hong Kong. Photo by Chung Yun Tak, extracted from ScienceDaily.

The results indicate that there is indeed an increase in predation rates towards the equator, as well as towards the sea level. Areas close to the poles or at high elevations have a smaller number of interactions. But even more interesting was the revelation that this change is really driven by small predators, especially arthropods such as ants. The rate of attacks by birds and mammals was fairly constant across the globe.

Such an evidence on the importance of arthropod predators at the tropics may make us reevaluate our ideas on the evolution of species in such places, as the main concern for small herbivores such as caterpillars in tropical forests may not be birds, but ants. And this means a completely different way to evolve defense strategies.

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Roslin, T., Hardwick, B., Novotny, V., Petry, W., Andrew, N., Asmus, A., Barrio, I., Basset, Y., Boesing, A., Bonebrake, T., Cameron, E., Dáttilo, W., Donoso, D., Drozd, P., Gray, C., Hik, D., Hill, S., Hopkins, T., Huang, S., Koane, B., Laird-Hopkins, B., Laukkanen, L., Lewis, O., Milne, S., Mwesige, I., Nakamura, A., Nell, C., Nichols, E., Prokurat, A., Sam, K., Schmidt, N., Slade, A., Slade, V., Suchanková, A., Teder, T., van Nouhuys, S., Vandvik, V., Weissflog, A., Zhukovich, V., & Slade, E. (2017). Higher predation risk for insect prey at low latitudes and elevations Science, 356 (6339), 742-744 DOI: 10.1126/science.aaj1631

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Filed under Ecology

Friday Fellow: ‘Abundant Yellow-Striped Flatworm’

by Piter Kehoma Boll

ResearchBlogging.org Today our Friday Fellow is an almost unknown species from an almost unknown group: Luteostriata abundans (formerly Notogynaphallia abundans) is a land planarian (a flatworm) found in southern Brazil, mainly in urban areas. It’s common to find it around in gardens and parks, hidden under leaves, stones and logs.

Two planarians Luteostriata abundans, named by me as Pierre and Marie (don’t forget they are hermaphrodites, though). Photo by Piter Kehoma Boll.

Most land planarians are very poorly known, even though they are recognized as good bio-indicators of conservation. However, there is an article published about the feeding habits of L. abundans (Prasniski & Leal-Zanchet, 2009). Currently it’s only known that it feeds on woodlice, but since it’s a very common species in disturbed areas, its diet probably includes something else. (I’m studying the predatory behavior of this and other species, but haven’t found any other prey item for it yet…)

Here at IPP (Instituto de Pesquisa de Planárias, in English “Planarian Research Institute”), we are also doing research about the regeneration of L. abundans. Everybody knows how well freshwater planarians can regenerate when cut into several pieces. Land planarians don’t seem to be so skilled, but very little is known about them on this subject too!

Another interesting fact that we noticed about L. abundans is their ability to escape from almost every container you put them into. We need to seal the lid of their plastic containers with adhesive tape and yet they sometimes manage to find a way to leave.

There is so much yet to know about these flatworms. As predators, they are essential to balance the population size of their prey in conserved areas and for those species known to live well in urban places, knowledge of their feeding habits is important to evaluate their chance to become invasive.

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Carbayo, F. 2010. A new genus for seven Brazilian land planarian species, split off from Notogynaphallia (Platyhelminthes, Tricladida) Belgian Journal of Zoology, 140 (Suppl.), 91-101

Prasniski, M. E. T. & Leal-Zanchet, A. M. 2009. Predatory behavior of the land flatworm Notogynaphallia abundans (Platyhelminthes: Tricladida) Zoologia, 26, 606-612 DOI: 10.1590/S1984-46702009005000011

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Filed under Behavior, Friday Fellow